The invention relates to a data input board for the electrical detection of the coordinates of a writing tip, comprising a rigid plate and an elastic plate each having an electrically conductive surface. The conductive surfaces are arranged electrically isolated at a small distance opposite each other by means of a frame-shaped spacer, and come in contact point by point under the impact of the writing tip on the outside of the elastic plate.
Japanese Patent Application No. 60-150124 describes such a data input board with transparent areal electrodes (i.e., electrodes having a superficial extent), the space provided by the frame being sealed between the areal electrodes and being filled with an insulating, viscous substance.
Further, a data input board is known from European Patent Application No. 0 194 861 comprising a conductive grid between the conductive surfaces kept at a distance by means of a frame.
Such data input boards are used in order to detect the coordinates of a writing tip, for example a pencil, acting with writing pressure upon the input surface of the board and in order to provide the coordinates for electronic processing, for example the representation on a screen (West German laid open application No. 36 02 061). In order to keep the opposite, electrically conductive surfaces at a distance without the effect of the writing tip, such devices are provided with spacers which may be formed as points or lines, for example, and are distributed over the input surface.
Those portions of the input surface which are directly associated to such spacers cannot be used for the detection of coordinates.